Acoustical apparatus



Feb. 25, 1947. KLElN 2,416,324

ACOUSTICAL APPARATUS Filed July 16, 1936 IN 51w Klein ATTORNEY Patented Feb. 25, 1947 UNITED STATES PATENT OFFICE. A

ACOUSTICAL APPARATUS Elias Klein, Washington, D. C. Application July 16, 19 36,Serial No. 90,937

22 Claims. (01. Isl -0.5)

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O; G. 757) My invention relates broadly to an acoustical apparatus for transmitting and/or receiving sound in a fluid medium such as water and in fluid media having similar acoustical properties.

It is an object of my invention to provide an acoustical apparatus which will transmit and/or receive sound with a minimum of attenuation.

It is a further object of my invention to provide an acoustical apparatus of high acoustical efiiciency for transmitting and/or receiving sound in a fluid medium, the said apparatus being impervious to the medium of propagation.

It is also an object of my invention to provide an apparatus of high acoustical efiiciency for transmitting and/or receiving sound in a fluid medium, the electro-acoustical transmitting and/or receiving means of which is not susceptible of becoming easily deranged.

My invention further resides in the provision of a fluid impervious, acoustically permeable housing for inclosing the sound transmittin and/or receiving means.

It is also an object of my invention to provide an acoustically permeable housing for inclosing the sound transmitting and/or receiving means and for electrically insulating the same.

These and further objects will be readily appreciated as the invention becomes better understood by reference to the following detailedspecification and drawings, wherein:

Fig. l is a sectional view of the housing with the closure member omitted;

and,

Fig. 3 is a view in section of the complete housin assembled with an acoustical instrumentality of one type.

When sound waves are traveling in a given medium and suddenly encounter another medium.

they will be reflected, absorbed, and transmitted atthe boundary in varying amounts depending upon the relative physical characteristics of the two media. For example, in transmitting sound 1 from air to water or vice versa, there-is practically complete reflection On the other hand, when sound waves pass from water into wood only about 15 per cent of the energy is reflected, and 85 per .cententers the wood. If, therefore, an efficient acoustical apparatus is desired, it is necessary that lithe sound transited side or face of the housing which incloses the acoustical instrumentality and 1 which separates the same from the medium of Fig. 2 is a view in front elevation of the housing; I

propagation shall be of a material which neither which embodies these characteristics is said to b sound-transparent. This desideratuin of soundtransparency is attained when the acoustical properties of the material in question'are substantially equal to those of the fluid medium in contact" therewith. The acoustical properties or impedances of two materials are alike or difierent depending upon whether the product of the density and the sound velocity in them is alike or difierent.

With a view to affording the acoustical instrumentality a maximum of protection and to insureits continued operation, it is essential that the" housing for inclosing the instrumentality shall be impervious to the medium of propagation, particularly where the apparatus is subaqueously employed. Furthermore, it is important when using an electro-mechanical sound transmitting or re ceiving means that internal electrical troubleswhich are directly traceable to the housing or to the fluid medium contained therein shall be eliminated. The invention contemplates the provision of an acoustical apparatus embodying the desirable and essential features discussed. v

Turning now to the drawings, there is shown in Fig. 3 the complete assemble-d acoustical ap-' paratus wherein the reference character I denotes the housing in general, 2 the acoustical instrumentality, and 3' a fluid medium immersing said instrumentalityconcerning which further details will be set forth hereinafter. The acoustical instrumentality may be either a sound transmit-'- ting means, a sound receiving means, or a means combining both of these functions. Although I" have shown the acoustical instrumentality 2 as being of an electro-mechanical type wherein 'electrical energy is transformed into sound energy in the transmitter or sound energy is transformed into electrical energy in the receiver, I do not desire to be limited thereto, since any type of acoustical instrumentality may be employed within the purview of my invention.

The housing I as shown in section in Figs. 1 and 3 includes an annular metallic member l of any suitable metal open at both ends. The annular member is lined interiorly at 5 and ex teriorly at 6 with a material to be described more in detail hereinafter and is closed at one side by the closure member 1 through suitable'securing means 8 and. at the other side by the sound permeable face. or window 9' whichis integral with the lining material.

As a material for the sound window 9, I may use any substance which has an acoustical ime pedance substantially equal to that of the fluid m dium in which the said substance is imme d While many of these materials will readily suggest themselves to those skilled in the art, I have found that certain rubber compounds may be conveniently used for this purpose. The general types of soft vulcanized rubber, for example, when immersed in water or in another liquid having similar acousical properties will transmit compressional, longitudinal sound waves, the degree of transmission varying considerably with the compound used. The closer the acoustical impedance of the compound matches that of the medium in which it is immersed, the more efiiciently it will act as a sound window. Any one familiar with the physical propertie required for sound transmission and versed in the art of compounding and processing elastic, resilient insulat- -ing substances will readily perceive the many compounds which can be made from rubber alone.

Since the acoustical impedance of the sound window 9 is substantially equal to that of the medium of propagation contacting therewith, it should be clear that the material of the window does not operate as a diaphragm and that the thickness of the window material in no way influences the frequency or function of the acoustical instrumentality within the housing and ad- :Iacent the sound window thereof.

The material lining the annular metallic member 4 at 5 and 6 and the window material should be such as to be impervious to the fluid medium surrounding the housing. Many such materials will suggest themselves to those skilled in the art, any of the types of rubber compounds heretofore discussed being particularly suitable for this purpose in view of their well known fluid impervious characteristic. In order, however, to make absolutely certain that the housing will be impervious to the fluid medium surrounding the same and contacting the exterior thereof, I have placed therein a fluid medium 3 which will not deleteriously aflect the acoustical instrumentality and which at the same time is air free, anhydrous, and of an acoustical impedance substantially equal to that of the fluid medium contacting the exterior of the housing. This medium within the housing may be oil or any equivalent material satisfying the requirements set forth and is under a pressure slightly in excess of the pressure of the fluid medium into which it is immersed. A few pounds of pressure above atmospheric pressure is usually sufficient to satisfy the requirement that the pressure of the fluid medium into which the housing and sound transparent window are immersed. Should the housing have any tendency to leak, it would be outward from within, thus protecting the inclosed acoustical instrumentality from detrimental contact with the fluid medium surrounding the housing. Since the pressure of the' fluid medium within the housin is greater than that of the fluid medium contacting the exterior, there is a tendency of the fluid medium within the housing to reinforce the sound transparent window 9.

The housing, according to my invention, is also constructed so as to reduce to a minimum any derangement of the acoustical instrumentality, particularly when it is of an electro-mechanical nature. Practically all modern under-water signaling devices are of an electro-acoustical nature. That is, electrical energy is transformed into sound energy in the transmitter or sound energy is transformed into electrical energy at the receiver; therefore, when the acoustical instrumentality is placed in the usual prior art metallic housing containing air or other gasepurposes without the payment of 4 ous medium, two difflculties may be encountered. The acoustical instrumentality may ground to the housing or condensation resulting from temperature changes may cause electrical leakage and impair the efiiciency of the electro-acoustical instrumentality, especially if it is a high voltage device. In order to avoid this prior art deficiency, I have chosen the material for lining both the interior 5 and the exterior 6 of the housing from the additional view point of its having high electrical insulatin qualities, many such materials occurring readily to those skilled in the art and the rubber compounds heretofore discussed being particularly suitable for the purpose because of the ease and economy with which they may be manufactured. Not only are the interior and exterior of the metallic annular member 4 lined with a material which has high electrical insulating properties, but also the closure member I is provided with an interior lining ill of similar characteristics. Thus, the interior of the completely assembled housing presents to the electro-acoustical instrumentality therein a highly: electrically insulating surface, thereby precluding any possibility of grounding the same. Furthermore, any possibility of condensation with attend-- ant electrical leakage is avoided by choosing the medium 3 within the inclosure such that it is air free, anhydrous, and of a high electrical insulat ing quality. Oil serves admirably for this purpose although many equivalent materials sati's-. fying the recited requirements may be used within the purview of my invention.

According to the provisions of the patent stat-- utes, I have set forth the principal mode of operation of my invention and have illustrated anddescribed what I now consider to represent its best embodiment. However, I desire to have it understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically illustrated and described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmentalany royaltiesthereon or therefor. 1'

I claim: 1. A housing adapted for use in a fluid medium v and for inclosing an acoustical instrumentality: adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprisin a fluid impervious inclosure at least one face of which is of a'material nonabsorbent to ultrasonic wave energy having an acoustical impedance substantiallyequal to that of the fluid medium in contact therewith. 2. A housing adapted for use in a fluid medium= and for inclosing an acoustical instrumentality, said housing comprising a fluid impervious in.-- closure at least one face of which is of a rubber compound having an acoustical impedance sub-- stantially equal to that of the fluid medium in: contact therewith. 3. A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressionalwave energy through said fluid medium, said 3 housing comprising a fluid impervious inclosure having at least one face thereof of a material 'nonabsorbent to ultrasonic wave energy and hay;-

wave energy through said fluid medium, said housing comprising a fluidimpervious inclosure having at least one face thereof of a material nonab sorbent to ultrasonic wave energy and having the portions of said housing exposed to the interior fashioned of an electrically insulating material.

' 5. A housing adapted for use in a fluid medium and forinclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprising a fluid impervious inclosure having the portions thereof exposed to the interior fashioned of a fluid resistant material and at least one face thereof fashioned of a material nonabsorbent to ultrasonic wave energy and having an acoustical impedance substantially equal to that of the fluid medium in contact therewith. -6; A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprising a fluid impervious inclosure having the portions thereof exposed to the interior fashioned of an electrically insulating material and at least one face thereof fashioned of a material nonabsorbent to ultrasonic wave energy and having an acoustical impedance substantially equal to that of the fluid medium in contact therewith.

'7. A housing adapted for use in a. fluid medium and for inclosing an acoustical instrumentality, said housing comprising a fluid impervious inclosure having the portions thereof exposed to the interior fashioned of a fluid resistant, electrically insulating material and at least one face thereof fashioned of a rubber compound having an acoustical impedance substantially equal to that of the fluid medium in contact therewith.

8. A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprising a fluid impervious inclosure having at least one face thereof of a material nonabsorbent to ultrasonic wave energy the interiorly exposed portions and at least a part of the exteriorly exposed portions of said housing being of a fluid resistant material.

9. A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprising a fluid impervious inclosure having at least one face thereof of a material nonabsorbent to ultrasonic wave energy the interiorly exposed portions and at least a part of the exteriorly exposed portions of said housing being of an electrically insulating material.

10. A housin adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housin comprising a fluid impervious inclosure having the interiorly exposed portions and at least a part of the exteriorly exposed portions of a fluid resistant material nonabsorbent to ultrasonic wave energy and at least one face thereof of a material having an acoustical impedance substantially equal to that of the fluid medium in contact therewith.

11. A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality adapted to transmit ultrasonic compressional wave energy through said fluid medium, said housing comprising a fluid impervious inclosure having the interiorly exposed portions and at least a part of the exteriorly exposed portions of an electrically insulating material nonabsorbent to ultrasonic wave energy and at least one face thereof of a material having an acoustical impedance substantially equal to that of the fluid medium in contact therewith.

12. A housing adapted for use in a fluid medium and for inclosing an acoustical instrumentality, said housing comprising a fluid im-' pervious inclosure having the interiorly exposed portions and at least a part of the exteriorly exposed portions of a fluid resistant, electrically insulating material and at least one face thereof of a rubber compound having an acoustical impedance substantially equal to that of the fluid medium in contact therewith.

13. Ahousing for acoustical instrumentalities comprising a, fluid impervious inclosure having a sound transparent window.

14. A housing for acoustical instrumentalities comprising a fluid impervious inclosure having a sound transparent window of a rubber compound.

15. A housing for acoustical instrumentalities comprising an annular metallic member lined both interiorly and exteriorly with a fluid resistant material and open at both ends, a closure in fluid tight engagement with one end of said metallic member, and a sound transparent window integral with said lining material and closing the other end of said metallic member.

16. A housing for acoustical instrumentalities comprisin an annular metallic member lined both interiorly and exteriorly with an electrically insulating material and open at both ends, a closure in fluid tight engagement with one end of said metallic member, and a sound transparent window integral with said lining material and closing the other end of said metallic member.

17. A housing for acoustical instrumentalities comprising an annular metallic member lined both interiorly and exteriorly with a fluid resistant, electrically insulating material and open at both ends, a closure in fluid tight engagement with one end of said metallic member and a sound transparent window fashioned of a rubber compound integral with said lining material and closing the other end of said metallic member.

18. An acoustical apparatus comprising in combination an acoustical instrumentality, a housing adapted for use in a fluid medium and for inclosing said acoustical instrumentality, said housing including a fluid impervious inclosure at least one face of which is sound transparent.

19. An acoustical apparatus comprising in combination an acoustical instrumentality, a housing adapted for use in a fluid medium and for inclosin said acoustical instrumentality, said housing including a fluid impervious inclosure at least one face of which is sound transparent, a second fluid medium within said inclosure which will not deleteriously affect the acoustical instrumentaliti housed therein and having an acoustical impedance substantially equal to that of the first mentioned fluid medium adapted to contact with the inclosure exterior, said second mentioned fluid medium being under a greater pressure than said first mentioned fluid medium whereby to reinforce the sound transparent face of the inclosure and preclude the entrance of the first mentioned fluid medium into the inclosure interior in the event the inclosure should develop a leak.

20. An acoustical apparatus comprising in combination an electro-acoustical instrumentality, a housing adapted for use in a fluid medium and for inclosing said instrumentality, said housing including a fluid impervious inclosure having the interiorly exposed portions thereof of an electrically insulating material and at least one face thereof of a material having an acoustical impedanoe substantially equal to that of the fluid medium in contact therewith, the interior of said inclosure being provided with an anhydrous fluid lnsulating medium of an acoustical impedance substantially equal to that of the first mentioned fluid medium adapted to contact with the inclosure exterior. v

21. An acoustical apparatus comprising in com, bination an acoustical instrumentality, a housing adapted for use in a fluid medium and for enclosing said acoustical instrumentality, said housing including a fluid impervious enclosure at least one face of which is operable to transit any sound energy incident thereupon, a second fluid medium within said enclosure which will not deleteriously aifect the acoustical instrumentality housed therein, said second mentioned fluid medium being under agreater pressure than said first mentioned fluid medium whereby to reinforce the sound transited face of the enclosure and preclude the entrance of the first mentioned fluid medium into the enclosure interior in the event the enclosure should develop a leak.

22. An acoustical apparatus comprising in combination an electro-acoustical instrumentality, a housing adapted for use in a fluid medium and for enclosing said instrumentality, said housing including a fluid impervious enclosure having the interiorly exposed portions thereof of an electrically insulating material and at least one face thereof operable to transit any sound energy incident thereupon, the interior of said enclosure being provided with an anhydrous fluid insulati-ng medium. .1

ELIAS REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,117,766 Berger Nov.17, 1914 1,121,986 Davison Dec. 22, 1914 1,463,507 Hahnemann July 31, 1923 

